The present invention relates to water-swellable polymers which polymers are useful in absorbing aqueous fluids.
Water absorbent materials comprising water-swellable polymers have provided various uses in the art. See, for example, U.S. Pat. Nos. 3,926,891; 4,190,562; 4,293,609 and 4,424,247. Numerous disposable articles containing such water-swellable polymers are disclosed as in U.S. Pat. Nos. 3,669,103 and 3,888,257.
Water-swellable polymers which are useful in providing absorbent materials are typically polymers comprising crosslinked acrylamide; hydrolyzed acrylamide; acrylic acid; hydrolyzed acrylates; hydrolyzed acrylonitrile; and grafted starch and celluloses; and the like. Such polymers require considerable care in controlling the amount of crosslinking which is present. For example, if the amount of crosslinking in the polymer is increased, the gel strength of the resulting polymer network is increased at the expense of reducing the capacity of the gel to absorb fluid. On the other hand, at low degrees of crosslinking the gels have a poor, slimy consistency which exhibit low gel strengths.
In view of the fact that the utility of known water-absorbent materials is limited due to lack of integrity of the gel structure during use, insufficient absorbing capacity and absorbing rate, and difficulties in crosslinking the polymers which are employed; it would be highly desirable to provide a novel, highly absorbent polymer system having a high gel strength and minimal amounts of crosslinking.